Antimony‐Based Lead‐Free Perovskite Thin Films for Highly Sensitive Ammonia (NH ₃ ) Gas Detection

Antimony (Sb)‐based perovskite materials have emerged as promising alternatives to Pb halide perovskites for gas‐sensing applications, offering reduced toxicity while maintaining high environmental sensitivity. Herein, we report a novel Sb‐based perovskite, formamidinium (FA) 3 Sb 2 Br 9 , as an environmentally friendly candidate for ammonia (NH 3 ) detection. FA 3 Sb 2 Br 9 can be synthesized via a simple solution‐based method, and it exhibits high selectivity and sensitivity toward NH 3 . Gas‐sensing measurements revealed that the device showed a markedly higher response to NH 3 than to other gases, such as NO x , CO, methanol, and methane. The device achieves a maximum gas response ( R = Δ I ( I t − I air )/ I air × 100 (%) = 235, at 100 ppm NH 3 ), with a short response/recovery time (13/289 s), a low detection limit of 1 ppm, and excellent reversibility. Furthermore, the FA 3 Sb 2 Br 9 sensor demonstrated a linear dependence on the NH 3 concentration, long‐term stability under ambient conditions over several months, and outstanding repeatability. These findings highlight the potential of Sb‐based perovskites as promising materials for high‐performance, Pb‐free NH 3 gas sensors.